Fluoride varnish is a concentrated form of fluoride applied to the teeth to help prevent cavities. It is a sticky substance that hardens when it comes into contact with saliva, allowing the fluoride to stay on the teeth longer. This treatment is often used in dental offices for both children and adults, especially those at higher risk for tooth decay. The application process is quick and painless. After cleaning the teeth, the dentist or dental hygienist paints the varnish onto the surfaces. Patients are usually advised to avoid eating or drinking for a few hours afterward to maximize the benefits of the fluoride.